1. Field of the Invention
The present invention relates generally to health equipment and, more specifically, to oxygen concentrators.
2. Description of the Related Art
Many patients require supplemental oxygen as part of Long Term Oxygen Therapy (LTOT). Currently, the vast majority of patients that are receiving LTOT are diagnosed under the general category of Chronic Obstructive Pulmonary Disease, COPD. This general diagnosis includes such common diseases as Chronic Asthma, Emphysema, Congestive Heart Failure and several other cardio-pulmonary conditions. Other people (e.g., obese individuals) may also require supplemental oxygen, for example, to maintain elevated activity levels.
Doctors may prescribe oxygen concentrators or portable tanks of medical oxygen for these patients. Usually a specific oxygen flow rate is prescribed (e.g., 1 liter per minute (LPM), 2 LPM, 3 LPM, etc.). Experts in this field have also recognized that exercise for these patients provide long term benefits that slow the progression of the disease, improve quality of life and extend patient longevity. Most stationary forms of exercise like tread mills and stationary bicycles, however, are too strenuous for these patients. As a result, the need for mobility has long been recognized. Until recently, this mobility has been facilitated by the use of small compressed oxygen tanks. The disadvantage of these tanks is that they have a finite amount of oxygen and they are heavy, weighing about 50 pounds, when mounted on a cart with dolly wheels.
Oxygen concentrators have been in use for about 50 years to supply patients suffering from respiratory insufficiency with supplemental oxygen. Traditional oxygen concentrators used to provide these flow rates have been bulky and heavy making ordinary ambulatory activities with them difficult and impractical. Recently, companies that manufacture large stationary home oxygen concentrators began developing portable oxygen concentrators, POCs. The advantage of POCs concentrators was that they could produce a theoretically endless supply of oxygen. In order to make these devices small for mobility, the various systems necessary for the production of oxygen enriched gas are condensed.
Oxygen concentrators may include a compressor that has reciprocating members, for example, piston compressors and wobble compressors. These types of compressors employ a series of valves to force the air to be pushed in one direction. Piston and/or wobble compressors may involve the acceleration of the reciprocating member followed by deceleration to a standstill, and then reacceleration in the opposite direction. Each of these changes of direction require energy and that energy is wasted usually exhibiting itself as heat and sound energy that is unwanted. Heat may damage the oxygen concentrator separation components (for example, molecular sieve beds). In the case of battery powered portable oxygen concentrators, heat dissipation may harm or shorten the life of the battery. For example, lithium ion battery that does not tolerate heat well and may have protect circuits that turn the battery off in the event of heat buildup.
Over a period of time, compressor valves maybe a source of component failure. The valves may lose their ability to check to reverse flow of the air passing through the compressor. Thus, causing compressor efficiency to diminish and the production of oxygen is reduced, resulting in less oxygen purity in the oxygen concentrator output. Thus, a compressor that has minimum and longer durability is desired.
Due to the rapid actuation of valves in traditional piston or wobble compressors, a vibration in the auditory range is inherent. The valves consequently emit unwanted noise. This noise may be at a frequency that is different from the frequency emitted by the pistons. As a result, there is an additive nature to the overall sound coming from the compressor. Thus, compressors that operate silently or do not emit frequencies in an auditory range are desired.
The weight of portable oxygen concentrators is important as the oxygen concentrator may be carried. Several factors may contribute to the weight of the device in general. Many of these factors related to the efficiency of the compressor used in the oxygen concentrator. For example, a less efficient compressor requires greater size of the compression mechanism to produce the required amount of compression. The larger the fluid chambers of the compressor, the more the compressor weighs. A less efficient compressor requires a much higher torque output to drive the compressor. Thus, the compressor motors may be larger and heavier. A less efficient compressor may require more power, and thus designed run time from a battery pack may require a bigger and heavier battery pack. Less efficient compressors may also include heavy subcomponents (for example, bearings, motors and valves), which adds cost in addition to weight to the compressor.
As described above, it is desirable to provide an oxygen concentrator that includes a durable, highly efficient and light-weight compressor.